Nanomaterials (NMs) find application in the biomedical and pharmaceutical area, the so-called
nanomedicinal products (NMPs). Once in the body, NMPs tend to end up in cells of the immune system.
Due to reported adverse effects on the immune system after NMPs administration, the immunotoxicity
profile of these products should be investigated. Information on the endotoxin levels in NMs and NMPs is
crucial for an appropriate interpretation of toxicity results, especially regarding immunotoxicity assays.
The aim of this review was to identify the assays that are available today for endotoxin determination in
NMs and NMPs and possible pitfalls as a result of the interaction of the testing samples with the assays.
Many of the currently available assays to determine endotoxin contamination were found to have limited
compatibility with NMs and NMPs due to interference, which is mostly related to their absorbance or
fluorescence properties and their strong tendency to adsorb biomolecules such as LPS and assay reagents
to their surface. Such interference of NMs and NMPs is not unique to endotoxin determination assays but
is also observed with various toxicity assays. Regarding the above, the availability of an assay to test
endotoxin presence without nanospecific interference is essential. In the meantime, use of appropriate
assay controls, producing and handling the NMs and NMPs in an endotoxin-free environment may be part
of the solution. In the absence of a single competent assay, it is more likely that a testing strategy of multiple
currently available assays will give reliable results.
Keywords: Endotoxin, immunotoxicity, testing, assessment, lipopolysaccharide, interference, nanomedicines.
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